Deck height issues.

[TucsonHooligan]

I have a '66 200 that I am having rebuilt. The block is at the shop right now, sans head due to cracks. I plan on getting a later model 200 head for the bigger valves and intake flow. Question is, what should the deck height be? I'm goin for a 9.0 compression ratio and figured I would zero deck it, but the machinist said he would have to take around .060 off to get it there, which seems like a lot. Would zero decking it raise the compression too much or what? I assumed a zero deck and the remainder taken off the head would get it done since the later model head have more cc's, but I'm worried about goin too far on the block and overshooting the compression. Suggestions?

 

[CZLN6]

Howdy Back:

.060" seems a little high Is he just guessing/estimating or measuring? Typically, stock OEM engines have the pistons down in the cylinder about .025". If you're using new, oversize pistons they will typically be .005" shorter too.

But, you can still zero deck the block when using a thicker composite head gasket and then determine how much to mill off the later head to get to your goal CR. The composite gasket is about .025" thicker then the OEM shim, so decking the block is just a trade off to get back to where you started. And the later head will be about 10 ccs more volume than the '66 head so you have another variable there. Have you checked into our site to run your numbers on the Compression calculator?

Adios, David

 

[TucsonHooligan]

He said he measured it. Seems a bit high to me as well. The pistons are oversize .060. So you're saying a zero deck isn't an issue, since I can use aftermarket gaskets to make up for any potential error? Even with a stock gasket, the higher cc's in the later head should give me enough wiggle room that the block won't be a boat anchor if I zero deck it? Can you provide a link to get to the calculator you're talking about?

 

[JackFish]

If you're putting new pistons in you could use some flat-tops to raise the CR.

 

[CZLN6]

Howdy back:

Unfortunately you can't get OEM steel shim head gaskets for the 200/250 any more. They have a compressed thickness of about .025". Currently available composite type gaskets measure about .050" thick. So decking the block .025" to .030" just gets you back to where you started. I decked my block .070" with no problems, so any less then that should be pretty safe.

Click on the highlighted link to our website in my signature. It is a heading on the left. Click on it. You will have to put in your figures to get accurate estimations. I ran some using a .060" overbore, zero deck height, .050" headgasket and a chamber volume of 54 ccs to get a 9:1 CR. If your late head has 62 cc chambers to start with, you will need to mill the head aproximately .040" to reduce chamber volumes to 54 ccs. But, as always- don't guess- MEASURE!!!

Adios, David

 

[mugsy]

I bought a used short block and one piston was 0.060 down the hole and the rest were 0.030". I found out that the rods were different cating numbers. The part numbers interchanged, but the rods were definetely different lengths AND weight.

Check the casting numbers on the rods; I found that the C1XX were shorter than the C3OE rods. Tha casting number (or whatever its called) is on the web, near the big end...

I had my block decked the 0.030 and used the thicker aftermarket head gasket. Plus took an additional 0.040 off the cylinder head to get into the 9.3:1 range.

tanx,
Mugsy 8)

 

[DupleDreux]

Hi,

speaking from my limited experiance, I'd wait until I had the head. I milled mine (head, ouch!) 060, but "at some time in the past" someone had already milled it 030, so it cc'd at 44, not 52. So I only milled about 010 off the deck (a cleanup) to get the compression right. Not too comfortable with multiple gaskets.

Beleive me I would have preferred to zero the block, but I didn't want to start over with the head.

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